Master Ansible: From Installation to Playbooks and Advanced Modules

Basic Deployment

Install Ansible

# yum -y install epel-release
# yum list all *ansible*
# yum info ansible
# yum -y install ansible

Ansible configuration files

/etc/ansible/ansible.cfg    Main configuration file
/etc/ansible/hosts          Inventory
/usr/bin/ansible-doc        Help files
/usr/bin/ansible-playbook   Playbook runner

Define Inventory

# cd /etc/ansible/
# cp hosts{,.bak}
# > hosts
# cat hosts
[webserver]
127.0.0.1
192.168.10.149

[dbserver]
192.168.10.113

Key‑based SSH connection

# ssh-keygen -t rsa
# ssh-copy-id -i /root/.ssh/id_rsa.pub [email protected]
# ssh-copy-id -i /root/.ssh/id_rsa.pub [email protected]
# ssh-copy-id -i /root/.ssh/id_rsa.pub [email protected]

Ansible command basics

# ansible-doc -l
# ansible-doc -s MODULE_NAME

Common modules

Examples include command, cron, user, group, copy, file, ping, service, shell, script, yum, setup and others. Each module’s parameters and typical usage are shown.

Ansible Playbooks

A playbook consists of one or more plays. Each play defines hosts, remote_user, variables, tasks, handlers, and roles. Tasks invoke modules with arguments; handlers are triggered by notifications; roles provide reusable components.

YAML Basics

YAML is a human‑readable data‑serialization format. It uses indentation, hyphens for lists, and colons for key‑value pairs. Example structures for scalars, lists, and dictionaries are provided.

Fundamental Elements

Variables

Variable names may contain letters, numbers and underscores, starting with a letter. Facts are gathered from remote hosts and can be accessed via ansible_facts. The register keyword stores task output for later use. Variables can be passed via --extra-vars or through roles.

Inventory

Inventory files group hosts, support host‑specific variables, group variables, and nested groups. Parameters such as ansible_ssh_host, ansible_ssh_port, ansible_ssh_user, etc., control connection details.

Conditional execution

Use when statements with Jinja2 expressions to run tasks only when conditions are met. Filters like failed, success, and skipped can be applied to registered results.

Loops

Iterate over items with with_items or newer loop syntax. Lists and dictionaries can be looped to create multiple resources.

Roles

Roles organize playbooks into reusable directories containing tasks, files, templates, handlers, vars, and meta. They can be included in a playbook with the roles keyword and accept parameters.

Tags

Tags allow selective execution of tasks. Use --tags with ansible‑playbook to run only tagged sections, and the special tag always forces execution.

Author: kangvcar Source: https://my.oschina.net/kangvcar/blog/1830155